Is only-child status associated with a higher blood pressure in adolescence? An observational study

Growing up with siblings may affect quality of life as well as hemodynamic parameters including blood pressure. Using weighted data from the nationwide and representative German KiGGs study, we assessed the relationship between only-child status, birth order, and arterial blood pressure in a cohort of 7311 adolescents aged between 11 and 17 years. Our data showed that only-children had the highest mean arterial blood pressure (87.3 ± 8.4 mmHg) as compared to first-born (86.3 ± 8.0), middle-born (86.4 ± 8.7), and youngest-born siblings (86.6 ± 8.2; p = 0.012). The two groups of only-children and first-borns differed significantly with respect to their age- and sex-specific, z-scored data for systolic (p = 0.047), diastolic (p = 0.012), and mean arterial blood pressure (p = 0.005). Linear regression models with blood pressure recordings as dependent variable adjusted to age, migration background, and age- and sex-specific z-scores of body-mass index confirmed that only-child status was an independent predictor of a higher diastolic blood pressure (p = 0.037). A similar result was observed for mean arterial blood pressure (p = 0.033), whereas systolic blood pressure was not associated with only-children status (p = 0.258).   Conclusion: In summary, we found a significant and positive relationship between only-child status and blood pressure, with the highest recordings in only-children and the lowest in first-borns. Models adjusted for relevant clinical confounders demonstrated slightly higher blood pressure in only-children compared to first-borns, who are both in an alpha birth order. Although these blood pressure differences were statistically significant, they have limited, if any, clinical meaning in this age group. What is Known: • In children and adults, blood pressure is significantly higher in only-children compared to children with siblings. However, it is unclear whether there are also similar blood pressure differences in adolescents and between only-children and first-borns. What is New: • Among adolescents in the alpha birth order, growing up as an only-child is associated with significantly higher mean blood pressure than among first-borns living with younger siblings.